The
concept of co-pyrolysis of biomass and conventional fossil
fuel offers various advantages such as higher liquid product yield
and higher char conversion than if the coal and biomass particles
were processed individually. In the case of added value fuel production
such as diesel and gasoline, the maximization of the fraction of pyrolysis
oil is the foremost objective. At the same time, the produced char
and permanent gases should be properly used for the isothermal and
stable operation of the pyrolysis process. This study presents an
integrated model of co-pyrolysis in ASPEN Plus for the production
of advanced hydrocarbons aiming to determine the conditions under
which the process performance is maximized. The methodology for the
design and modeling of each main unit of the system (i.e., the pyrolysis
plant, the oil upgrading unit, and char exploitation plant) is described
in detail. Simulation runs were performed for various blending ratios
from 0% to 100% of coal to biomass, aiming for the optimum design
and operation scheme regarding (a) maximization of the yields of the
desired products and (b) exploitation of the retrieved char. Simulation
results revealed that high yields of hydrocarbons (up to 0.179 kgHCs/kgfeed) can be produced due to the synergetic
effects of co-pyrolysis of coal and biomass. Moreover, the total process
efficiency when the rest of char is utilized for electricity and methanol
production can reach at 55.5% and 61.9%, respectively. Finally, the
energy balance calculations for the case of 60% coal blending ratio
showed that almost 30% of the initial heat input is used as heat for
pyrolysis and allothermal gasification of the char. Possible use of
alternative heat sources, e.g., from solar energy for these two processes
would further improve the system performance in terms of advanced
fuels productivity.